The invention relates to cup forming machines and more particularly to a method and apparatus for lubricating the upper edge of the cup blank prior to formation of the cup rim.
Automatic machines for making cups or other containers from paper stock are well known. Such machines may, for example, be used for preparing drinking cups for hot or cold liquids. The paper stock employed in such cup making machines may be coated on one or both sides with a resin material, such as polyethylene which serves to protect the paper stock from penetration by liquids.
In such cup forming machine the paper stock is provided as rolls from which the sidewall and bottom portions of the cup are cut by means such as blanking dies. After the sidewall blanks have been cut, they are transferred to a mandrel assembly where they are wrapped around a mandrel with overlapping edges which are then sealed with an adhesive or by the application of heat. The sidewall is clamped in position until the adhesive is set or the heated polyethylene has hardened. In the meantime, the bottom blanks are formed by a pressing die into a shallow cupped configuration and are then applied to the end of the mandrel holding the formed sidewall. Adhesive or heat may then be used to seal the bottom to the sidewall. The cup is then transferred to a rim forming station. Here, the cup is held by means such as a vacuum in a pocket while its upper end is engaged by tools which curl and then roll the edge back around itself to form the rim. Because of the high frictional forces which occur during the rim forming operation, prior art cup making machines applied a lubricant to the rim of the cup prior to the application of the rim forming tool. The lubricant was applied to the cup by means of a spray device or an annular wick after the formed cup was transferred from the forming mandrel to the vertically oriented rimming pockets.
Such prior art methods and apparatus for applying lubricant were found to be unsatisfactory because the lubricating material such as silicone or mineral oil tend to drip into the cup rendering them unsatisfactory.